Circuit breaker



Nov. 4, 1941. J. BEHRINGER C IRCUIT BREAKER Filed Nov. 7, 1939 WITNESSES: v

Patented Nov. 4, 1941 CIRCUIT BREAKER Joseph Behringer, Berlin-Friedrichsfelde, Germany, assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application November 7, 1939, Serial No. 303,285 In Germany November 7, 1938 17 Claims.

The invention relates to circuit breakers and more particularly to operating mechanisms of the hydraulic type for operating multipole or multiphase high voltage circuit breakers.

A number of diificulties have been encountered in the use of circuit breaker operating mechanisms of the hydraulic type, particularly in the case of multipole or multiphase high voltage circuit breakers. If liquid conducting tubes of small cross-section are used, the velocities of the moving liquid and with them the kinetic energy effects become large. Furthermore, the resistance to motion and the frictional resistance against the walls of the tubes also become large. One of the requirements of a satisfactory hydraulic system is that the kinetic effects of the liquid columns should be kept as low as possible. This requirement may be fulfilled by the use of liquid conducting tubes of larger diameter which cause the velocities of the moving liquid to be decreased, and consequently the kinetic energy effects to be also decreased, since the velocity plays the greatest roll as can be seen from the formula mp T Since the velocity of the liquid is thus decreased, the friction of the liquid against the walls of the tubes is also decreased so that the influence of greater viscosity at lower temperatures becomes smaller.

On the other hand, since the liquid or oil of the hydraulic system is somewhat compressible due to the presence of air therein, it is desirable to maintain the volume of liquid as small as possible to minimize the undesirable efiects of the compressibility of the liquid. In the case of multipole or multiphase high voltage circuit breakers in which the moving contact members are coupled hydraulically for simultaneous operation, the large volume of oil or liquid required for the hydraulic system does not permit the attainment of a sufiiciently rigid coupling due to the compressibility of the liquid.

The requirement of small liquid volume for minimizing compressibility thus to a certain extent directly confiicts with the requirement of larger diameter liquid conducting tubes for decreasing the kinetic energy effects and the frictional resistance.

The present invention provides for the attainment of both of the above mentioned requirement 1. e., the use of liquid conducting tubes of large diameter on the one hand, and the use of a relatively small volume of oil on the other hand.

An object of the invention is the provision of an improved hydraulic operating mechanism for a high voltage multipole circuit breaker, in which the moving contacts are sufiiciently rigidly coupled to insure their simultaneous movement, and in which the volume of oil used in the hydraulic drive is relatively small.

Another object of the invention is the provision of an improved hydraulic operating mechanism for a multiple circuit breaker which utilizes liquid conducting tubes of relatively large diameter thus decreasing the kinetic energy eifects of the liquid and the frictional resistance against the Walls of the tubes, and which at the same time utilizes only a relatively small volume of oil for the liquid drive.

A more specific object of the invention is the provision of an improved hydraulic operating mechanism for a multipole or multiphase circuit breaker, in which the moving contact member of each pole is provided with a separate liquid pressure actuated operating means with its own individual advancing device or oil pump, and in which the oil pumps are mechanically connected to each other and to a common driving device for simultaneous operation.

Another object of the invention is the provision of a hydraulic circuit breaker operating mechanism embodying separate and distinct liquid conducting tubes and advancing devices or oil pumps for each phase or pole.

Another object of the invention is the provision of a hydraulic circuit breaker operating mechanism as previously described in which each of the individual oil pumps or advancing devices is disposed in a closed chamber directly beneath and closely adjacent the supporting insulator of its corresponding phase, and in which each chamber communicates with the oil filled interior of the supporting insulator and serves as an expansion vessel.

Another object of the invention is the provision of a hydraulic circuit breaker operating mechanism as previously described, in which the closed expansion chamber surrounding each oil pump is connected through back pressure valves with the opposite ends of the cylinder of the oil pump, and through one of the oil conducting tubes and a check valve with a further oil filled expansion space provided in the outer jacket of the circuit interrupter.

Another object of the invention is the provision of a hydraulic circuit breaker operating mechanism as previously described in which the oil conducting tubes are of insulating material and disposed inside the oil filled supporting insulators of the breaker poles and maintain the live part insulated from ground.

Another object of the invention is the provision of an improved hydraulic operating mechanism for a high voltage multipole circuit breaker which is simple, reliable in operation, and inexpensive to manufacture.

The invention will be best understood from the following detailed description thereof when read in conjunction with the accompanying drawing, in which;

Figure l is a vertical sectional view of a multipole circuit breaker mechanism constructed in accordance with the invention; and

Fig, 2 is a fragmentary horizontal sectional view on a reduced scale of a modified construc tion of the circuit breaker operating mechanism, a portion of the supporting casing being broken away.

Referring to the drawing, the reference numerals 5, and 9 generally designate the individual units of the multipole high voltage circuit breaker structure. The units are supported in spaced relation upon a common metal casing or main support H, and are of identical construction, hence a description of one unit only will be given.

Each unit comprises two superposed tubular insulators I3 and I5 of vitreous insulating material separated by a metallic casing member I The upper insulator l3 provides a casing for a circuit interrupting means of one of the poles comprising a tulip type stationary contact IS, a cooperating vertically movable contact member 2|, and an arc extinguishing structure 23 of the expansion type. The are extinguishing structure may be of any conventional form as, for example, of the type shown and described in the copending application of Paul Duffing Serial No, 246,410, filed December 17, 1938, and assigned to the assignee of the present invention.

The movable contact member 2| in the casing member I! and is movable vertically into and out of engagement with the stationary contact H). A metal cap 25 is mounted on the upper end of the insulator l3 and this cap is provided with a terminal which is electrically connected to the stationary contact IS.

The other terminal of the pole unit is secured to the casing member l1 and is electrically connected in any suitable manner with the movable contact member 2|, preferably by conventional spring pressed stationary contact segments (not shown) which engage the contact member 2|.

A tubular insulating member 21 of strong insulating material is disposed inside of the upper insulator I3 and has its lower end sealed to the casing member H. The interrupting chamber within the tubular member 21, and the outer space 28 between the tubular member and the insulator l3 are both filled with a body of insulating liquid such as oil or the like, the tubular member 21 serving to separate the liquid in the interrupting chamber from the liquid in the outer space 28,

The lower insulator l5 which serves as a supporting insulator has its lower end secured and sealed to a flanged metal base 29 which is, in turn, secured in an opening provided in the metal casing A separate and distinct hydraulic operating mechanism is provided for each movable conextends 7 through a suitably packed liquid tight opening tact member. Each mechanism comprises a liquid pressure actuated operating means 3| disposed within the upper portion of the supporting insulator 5, a liquid actuating control pump 33 disposed immediately below the base 29 of the supporting insulator |5 for actuating the operating means 3| to open and close the contact member 2|, and a pair of liquid conducting tubes 35 and 31 of insulating material disposed in the supporting insulator I5 and connecting the liquid actuated operating means 3| with its corresponding control pump 33 only.

The liquid actuated operating means comprises a metal cylinder 39 and a piston 4| movable therein which is connected directly to the lower end of the movable contact member 2|. The upper end of the tube 31 is connected directly to the lower end of the cylinder 39 and serves to carry the operating liquid for closing the contact member 2|. The upper end of the tube 35 communicates with a space 43 which, in turn, communicates with the upper end of the cylinder 39, and this tube carries the operating liquid for opening the contact member The metal base 29 is preferably cast to provide an integral housing 45 which is disposed in the casing immediately below the base of the insulator l5. The housing 45 is closed at one end by closure cap 41 and at its other end by a filler plug 49 so that the housing closure cap forms a closed expansion chamber 5|, and this chamber communicates with the interior of the supporting insulator l5 through a passage 53. A body of insulating liquid such as oil is disposed in the supporting insulator l5 and in the expansion chamber 5|, and the head of this liquid forms a pressure air pocket in the upper portion of the chamber 5| directly under the base of the insulator 5.

Each liquid actuating control pump 33 comprises a pump cylinder 51 which is disposed inside the housing 45 and completely immersed in the liquid in the expansion chamber 5|. The pump cylinder 51 is preferably formed integral with the housing 45 although not necessarily so.

A pump piston 59 is movable back and forth within the cylinder 5'! for moving the operating liquid to operate the movable contact member 2| to open and closed circuit position. The operating liquid which fills the hydraulic system is the same as the liquid in the outer space 28 of the interrupting device and in the insulator l5 and chamber 45. This liquid may be oil or other suitable insulating liquids such as chlorized or fluorized hydrocarbons. The pump cylinders 51 and pistons 59 may be constructed as simple pistons, or as differential pistons as shown.

The lower ends of the insulating tubes 35 and 31 communicate with the cylinder spaces on opposite sides of the pump piston 59 through passages GI and 63 provided in the housing 45 and cylinder 51.

Each pump piston is adapted to be moved towards the left to effect opening of the breaker by means of a separate circuit opening spring 65 which is disposed in the liquid in the chamber 5| and has one end abutting the end of the cylinder 5'! and its other end engaged with a collar 61 secured to the connecting rod 69 of the pump piston 59.

The pump pistons 59 are mechanically connected with each other for simultaneous movement together through the agency of the double arm cranks II and one or more connecting rods I3, and connected with a common driving a pin and slot connection 83.

device 15 which serves for closing the breaker by means of a connecting rod 11.

Each crank 1| comprises a shaft 19 which extends transversely into the closure cap 4.] of the housing 45 through a liquid tight bushing, and is rotatably mounted in the cap. One arm 8| of the crank is secured to the shaft inside of the cap 4'! and is pivotally connected to the end of the piston connecting rod through the agency of The other arm 85 of the crank 1| is secured to the portion of the shaft 19 outside of the closure cap 41. The free ends of the crank arms 85 are pivotally connected to connecting rod 13. The crank ll of the lefthand unit 5 is provided with an additional crank arm 81 rigid with the shaft 19, and the arm 81 is pivotally connected to one end of the rod 11 for actuation by the common driving device 15.

The driving device 15 is of the air pressure operated type and comprises an air pressure cylinder 89 secured to the casing II, and a piston 9| movable therein which is pivotally connected to the rod H. A source of compressed air and control Valve (not shown) are connected to the left-hand end of the cylinder 89 through the opening 9-2 for actuating the piston 9| to effect closing of the breaker. A conventional latch 94 and electromagnetic tripping means 96 are provided for releasably holding the breaker in closed position against the bias of the circuit opening springs 55.

When air under pressure is admitted to the left-hand end of the cylinder 89, the piston 9| is moved inwardly effecting simultaneous movement of the three pump pistons to the right, since they are rigidly mechanically coupled with each other and with the air pressure operated driving piston 9!. This simultaneous movement of the three pump pistons causes a flow of liquid upwardly in the tubes 31 effecting simultaneous upward movement of the three operating pistons 4| thereby simultaneously moving the three contact members 2| to closed circuit position into engagement with the stationary contacts. The liquid above the operating pistons 4| in the cylinders 39 will be displaced during the upward movement and caused to flow out of the cylinders 39 into the tubes and into the left-hand end of the pump cylinders 51. The latch 94 engages a latch projection on the crank arm 81 and releasably maintains the breaker in closed position against the bias of the circuit opening springs 65.

When the latch device 94 is released in response to energization of tripping electromagnet 96, the three pump pistons 59 are moved to the left by their circuit opening springs 65. This opening movement of the pump pistons takes place simultaneously since they are rigidly mechanically coupled with one another by the connecting rod or rods 13. During this opening movement the rod or rods 13 merely act as a coupling between the pumps and hence do not transfer any appreciable force. Hence the rod or rods l3 may be made relatively light since they only transmit tensional forces. The opening movement of the three pump pistons causes liquid to flow upwardly in the tubes 35 causing the three operating pistons 4| to be moved downwardly simultaneously thereby moving the three contact members 2| downwardly to open circuit position as shown in Fig. 1. The liquid in the cylinders 39 below the operating pistons 4| is caused to flow downwardly into the tubes 31 and intov the right-hand ends of the pump cylinders 51.

By having a separate and distinct complete hydraulic operating mechanism for each pole of the breaker with the liquid actuating control pumps thereof located immediately below the supporting insulators of their corresponding poles, i. e., close to the contact operating pistons, and the control pumps mechanically connected for simultaneous movement, the volume of operating liquid required for the breaker is kept relatively small, much smaller than for hydraulic systems where the phases are coupled hydraulically. Since the volume of operating liquid is small, this materially decreases the undesirable effects resulting from the compressibility of the operating liquid. Furthermore, the material reduction in the volume of operating liquid thus afforded by the construction permits the use of liquid conducting tubes of larger diameter or size, thereby decreasing the kinetic energy effects and the frictional resistance against the walls of the tubes.

Since the liquid conducting tubes 35 and 3i within the supporting insulators are of insulating material and the operating liquid therein is also of high dielectric strength, the insulating path within the supporting insulators which are filled with oil is maintained or preserved by the tubes 35 and 3! and the operating liquid therein, so that the individual control pumps 33 can safely be located in the immediate vicinity directly at the base of the supporting insulators.

In each pole, the insulating liquid in the expansion chamber 5| and in the supporting insulator I5 is connected with the opposite cylinder spaces of the pump cylinder 51 through the agency of back pressure or non-return valves 99 and 95, respectively, whereby the operating liquid in the cylinders 39 and 5'! and in the tubes 35 and 31 is always maintained under a static pressure greater than atmospheric pressure, thus pre venting any air dissolved in the operating liquid from separating out of the liquid. The Valves 93 and 95 also permit expansion of the operating liquid, since during expansion the change in volume takes place slowly so that the valves do not entirely close. The valves 93 and 95 close to prevent the b-ack flow of liquid out of the cylinder 51 during operation of the breaker since during operation the changes in pressure and flow of liquid take place rapidly.

In each pole a check valve 9'! is provided in the space 43 for connecting the liquid in the space 28, between the tubular insulating member 21 and the insulator I3, with the upper end of the liquid conducting tube 35. The check valve 91 closes during operation of the breaker due to the rapid increase in pressure and prevents the back flow of liquid from the tube 35 into the space 28. The valve 91, however, is constructed to close only in response to a rapid increase in pressure such as arises during operation of the breaker. The construction and arrangement of the valves 93, 95 and 91 provides for a substantially air free filling of the entire apparatus through the filler plugs 49; and causes the liquid conducting tubes 35 and 3'! and the cylinder spaces themselves to remain air free after a plurality of switching throws. The insulating liquid is filled through the expansion chambers 5| and rises in the insulators l5, and through the back pressure valves 93 and 95, in the cylinders 51 and the insulating liquid conducting tubes 35 and 31, and through the check valve 91 to the expansion spaces 28 in the upper insulators l3.

Fig. 2 shows a modification of the invention with reference to the coupling between the poles. The structure is substantially the same as the embodiment shown in Fig. 1 except that the pump pistons of the control pumps are mechanically connected for simultaneous movement together through the agency of a rotatable shaft 99 common to the three phases of the breaker. The shaft 99 extends transversely through the closure caps 4'! of each housing 45 and has crank arms 81 rigidly secured thereto inside of the closure caps 47 which are pivotally connected to the connecting rods 69 of the pump pistons by the pin and slot connections. A single crank arm 81 is secured to the shaft 99 outside of the caps 41 and this crank arm is pivotally connected to the rod H and through the same to the air pressure operated piston 95. The remaining structure and the operation of the breaker is identical to the embodiment shown in Fig. l and described in connection therewith.

An electric motor, solenoid or any other desired type of drive may be substituted for the cornpressed air driving device 15. Also the driving device may be arranged to operate the pump pistons in both directions if desired, in which instance the springs 65 may be omitted.

While the invention has been disclosed in accordance with the provisions of the patent statutes, it is to be understood that various changes in the structural details thereof may be made without departing from the spirit of the invention. It is desired, therefore, that the appended claims be given the broadest reasonable interpretation permissible in the light of the prior art.

I claim as my invention:

1. In combination, a multipole circuit breaker having a movable contact member for each pole, a separate and distinct complete hydraulic operating mechanism for each contact member, each hydraulic mechanism having a separate and distinct control pump; and mechanical means connecting said control pumps to each other and to a common driving device for simultaneous operation.

2. In combination, a multipole circuit breaker having a movable contact member for each pole, a separate liquid actuated operating means for each contact member, a plurality of separate liquid actuating pumps, one for each pole for controlling the movement of said operating means, separate liquid conductors connecting each operating means and its separate liquid actuating pump only, and means mechanically connecting said liquid pumps with each other and with a common driving device for simultaneous operation.

3. In combination, a multipole circuit breaker having a movable contact member for each pole, a separate liquid actuated operating means for each contact member, a plurality of liquid actuating control pumps, one for each pole for controlling the movement of said operating means, separate liquid conductors connecting each operating means to its corresponding control pump only, each control pump being disposed closely adjacent its corresponding operating means, and means mechanically connecting said control pumps to each other and to a common driving device for simultaneous operation.

4. In combination, a multipole circuit breaker having a movable contact member and a hollow supporting insulator for each pole, a separate liquid actuated operating means for each contact member, a, plurality of liquid actuating control pumps, one for each pole for moving said operating means, a pair of liquid conductors of insulating material disposed in each supporting insulator and connecting said operating means to its corresponding control pump only, and means mechanically connecting said control pumps to each other and to a common driving device for simultaneous operation.

5. In combination, a polyphase circuit breaker having a movable contact member and a hollow supporting insulator for each phase, a separate liquid actuated operating means for each contact member, a plurality of separate liquid actuating control pumps, one for each phase for moving said operating means, each control pump being disposed immediately adjacent the base of the insulator of its corresponding phase, a pair of liquid conductors of insulating material disposed in each supporting insulator and connecting said operating means to its corresponding control pump only, and means mechanically connecting said control pumps to each other and to a common driving device for simultaneous operation.

6. In combination, a polyphase circuit breaker having a movable contact member and a hollow supporting insulator for each phase, a separate liquid actuated operating means in each supporting insulator for each contact member, a separate liquid actuating control pump for each phase for moving said operating means, each of said control pumps being disposed immediately below and closely adjacent the base of the supporting insulator of its corresponding phase, liquid conducting tubes of insulating material and of relatively large size disposed inside said supporting insulators and connecting said operating means to their corresponding control pumps, and means mechanically connecting said control pumps to each other and to a common driving device for simultaneous operation.

7. In combination, a multipole circuit breaker having a movable contact member for each pole, a separate liquid actuated operating means for each contact member, a plurality of liquid actuating control pumps one for each pole for controlling the movement of said operating means, separate liquid conductors connecting each operating means to its corresponding control pump only, each control pump being disposed closely adjacent its corresponding operating means, and means mechanically connecting said control pumps to each other and to a common driving device for simultaneous operation, said control pumps each comprising a differential piston and cylinder.

8. In combination, a polyphase circuit breaker having a movable contact member and a hollow supporting insulator for each phase, a separate liquid actuated operating means in each supporting insulator for each contact member, a separate liquid actuating control pump for each phase for moving said operating means, each of said control pumps being disposed immediately below and closely adjacent the base of the supporting insulator of it phase, liquid conducting tubes of insulating material and of relatively large size disposed inside said supporting insulators and connecting said operating means to their corresponding control pumps, and means mechanically connecting said control pumps to each other and to a common driving device for simultaneous operation, said control pumps each comprising a differential piston and cylinder.

9. In combination, a polyphase circuit breaker having a movable contact member for each phase, a separate liquid actuated operating meansfor each contact member, a separate liquid actuating control pump for each phase for moving said operating means, separate liquid conductors connecting each of said operating means to its separate liquid actuating pump only, means mechanically connecting said pumps to each other and to a common driving device for simultaneous operation, and a separate circuit opening spring for each control pump for actuating said control pumps to effect opening of the breaker whereby said mechanical connecting means serve only for coupling said pumps during opening of the breaker and do not transfer any substantial force.

10. In combination, a polyphase circuit breaker having a movable contact member and a hollow supporting insulator for each phase, a separate liquid actuated operating means for each movable contact member, a separate liquid actuating control pump for each phase for actuating said operating means, each control pump being disposed immediately below and closely adjacent the base of the supporting insulator of its corresponding phase, a pair of liquid conductors of insulating material disposed in each supporting insulator connecting each operating means to its corresponding control pump only, and means mechanically connecting said control pumps to each other and to a com mon driving device for simultaneous operation, said mechanical connecting means coupling said pumps comprising one or more light tension rods.

11. In combination, a polyphase circuit breaker having a movable contact member and r a hollow supporting insulator for each phase, a separate liquid actuated operating means for each movable contact member, a separate liquid actuating control pump for each phase for actuating said operating means, each control pump being disposed immediately below and closely adjacent the base of the supporting insulator of its corresponding phase, a pair of liquid conductors of insulating material disposed in each supporting insulator connecting each operating means to its corresponding control pump only, and means mechanically connecting said control pumps to each other and to a common driving device for simultaneous operation, said mechanical connecting means which couple said control pumps comprising a common rotational shaft.

12. In combination, a polyphase circuit breaker having a movable contact member and a hollow supporting insulator for each phase, a separate liquid actuated operating means for each movable contact member, means forming a closed expansion chamber immediately below and closely adjacent the base of each supporting insulator, each expansion chamber communicating with the interior of its corresponding supporting insulator, a body of insulating liquid in each supporting insulator and expansion chamber, the liquid forming an air cushion in the upper portion of each expansion chamber, a separate liquid actuating control pump for each phase disposed in said expansion chambers for actuating said operating means, a pair of liquid conducting tubes of insulating material disposed in each supporting insulator connecting each operating means to its corresponding control pump only, and means mechanically connecting said control pumps to each other and to a common driving device for simultaneous operation.

13. In combination, a polyphase circuit breaker having a movable contact and a hollow supporting insulator for each phase, a separate liquid actuated operating means for each contact member, means forming a closed expansion chamber immediately beneath and adjacent the base of each supporting insulator, each expansion chamber communicating with the interior of its corresponding insulator, a body of insulating liquid in each supporting insulator and expansion chamber, said liquid forming an air pocket in the upper portion of each expansion chamber, a plurality of liquid actuating control pumps one for each phase disposed in said expansion chambers for actuating said operating means, a pair of liquid conductors in each supporting insulator connecting each operating means to its corresponding control pump only, a separate circuit opening spring for each control pump disposed in each expansion chamber for actuating said control pump to open circuit position, and means mechanically connecting said control pumps to each other and to a common driving device for simultaneous operation, said control pumps and circuit opening springs being disposed in the liquid in said expansion chambers.

14. In combination, a polyphase circuit breaker having a movable contact member and a hollow supporting insulator for each phase, a separate liquid actuated operating means for each movable contact member, means forming a closed expansion chamber immediately beneath and adjacent the base of each supporting insulator, each of said chambers communicating with the interior of its corresponding supporting insulator, a body of insulating liquid in each supporting insulator and expansion chamber, the liquid forming a pressure air pocket in the upper portion of each expansion chamber, a plurality of liquid actuating control pumps one for each phase for actuating said operating means, said pumps being disposed in said expansion chambers and each comprising a pump cylinder and piston, a pair of liquid conducting tubes of insulating material disposed in each supporting insulator connecting each operating means to the opposite ends of its corresponding pump cyl- 4 inder only, means including back pressure valves connecting each expansion chamber with the cylinder spaces of its associated control pump for maintaining the liquid of said hydraulic drive under a pressure greater than atmospheric and to permit expansion and contraction of the driving liquid, and means mechanically connecting said pump pistons to each other and to a common driving device for simultaneous actuation.

15. In a polyphase circuit breaker, a plurality of housings one for each phase, each comprising a pair of superposed tubular insulator columns, a metallic casing member between said columns dividing said housing into upper and lower compartments, a tubular member of insulating material disposed within the upper compartment having its lower end sealed to said casing member, a body of insulating liquid disposed between said tubular member and the upper insulator column, a movable contact member in each housing extending through said casing member, a separate liquid actuated operating means in each housing for each movable contact member, means forming a closed expansion chamber immediately beneath and adjacent the base of each housing communicating with the lower compartment of its corresponding housing, a body of insulating liquid in the lower compartment and expansion chamber of each housing, a separate liquid actuating pump cylinder and piston for each phase for actuating said operating means, said pump cylinders being disposed in said expansion chamber, a pair of liquid conducting tubes of insulating material in the lower insulator column of each housing for connecting each operating means to the opposite ends of its corresponding pump cylinder, means comprising back pressure valves connecting each expansion chamber with the cylinder spaces of its corresponding pump cylinder and through one of said liquid conducting tubes and a check valve with the liquid in the space between the upper column and the tubular member to provide for air free filling of liquid into said breaker through said expansion chambers and to maintain th actuating liquid under a pressure greater than atmospheric pressure and to permit expansion thereof, and means mechanically connecting said pump pistons to each other and to a common driving device.

16, In a polyphase circuit breaker, a plurality of tubular insulator housings one for each phase, each divided into upper and lower compartments by a metallic casing member, a tubular member of insulating material disposed in the upper compartment of each housing and having its lower end sealed to said casing member, a body of oil in the spac between said tubular member and the wall of said housing, a movable contact member in each housing extending through said casing member into said tubular member, a separate liquid actuated operating means for each movable contact member, means forming a closed expansion member immediately below and adjacent the base of each housing which chamber communicates with the lower compartment of said housing, a body of insulating liquid in the lower compartment and expansion chamber of each housing, a separate liquid actuating control pump comprising a pump cylinder and piston for actuating each operating means, said control pumps being disposed in said expansion chambers, a pair of liquid conducting tubes of insulating material disposed in the lower compartment of each housing for connecting each operating means to the opposite ends of its corresponding pump cylinder only, means including back pressure valves connecting each expansion chamber with the opposite cylinder spaces of the pump cylinder therein and through one of said pair of liquid conducting tubes and a check valve with the space between said tubular member in the upper compartment and the wall of said housing, and means mechanically connecting said pump pistons with each other and with an air pressure operated driving device for simultaneous operation.

17. In combination, a polyphase circuit breaker having a movable contact member for each phase, a hollow supporting insulator for each phase secured and sealed at its lower end to a flanged metal base, said metal base being provided with a closed housing beneath said supporting insulator which communicates with the interior of said supporting insulator and forms an expansion chamber, said housing having at least a part thereof formed integral with said base, a body of oil in said Supporting insulator and housing forming a pressure air pocket in the upper portion of said housing, a separate liquid actuated operating means for each movable contact member, a separate liquid actuating control pump for each phase for actuating said operating means comprising a pump cylinder and piston disposed in the oil in each of said housings, a pair of liquid conducting tubes of insulating material disposed in each supporting insulator connecting each operating means to the opposite end of its corresponding pump cylinder, means comprising back pressure valves connecting each expansion chamber with the opposite cylinder spaces of the pump cylinder disposed therein whereby the oil in said supporting insulator and expansion chambers maintains the liquid in said operating means, tubes, and pump cylinders under a pressure greater than atmospheric pressure and permits expansion and contraction thereof, and means mechanically connecting said pump pistons with each other and with a common driving device for simultaneous operation.

JOSEPH BEHRINGER. 

